1. Field of the Invention
The present invention relates to devices for collecting fluid samples or injecting medications or assessing the degree of inflation of balloon-tipped catheters or endotracheal tubes and more particularly to a bladder-type syringe in which not only is the amount of air, which will contaminate a portion of the fluid sample, therein minimized, but also the contaminated portion of the fluid sample may be separated from its uncontaminated remaining portion.
2. Description of the Prior Art
Human blood samples have long been collected for various medical tests. In recent years, gas-tension analysis of blood has become one of the most important laboratory tests in the management of patients with respiratory and metabolic disorders by measuring the partial pressures of dissolved oxygen and carbon dioxide in the circulatory system. However, the collection of a satisfactory blood sample from a patient for analysis has posed a number of difficulties. Initially in some patients it may be somewhat difficult to ascertain whether the collection device has received arterial or venous blood without differentiating "fill pressures" during collection. Second, the collection device should minimize contact of the blood sample with air since the air may affect the results of blood analysis. It is also desirable that the sample should not be collected in the presence of a vacuum, since it is believed that the vacuum may modify the gas-tension characteristics of the sample. The collection device should also be in a suitable form to permit closure of the sample to air and provide thermal characterisitics which promote rapid chilling of the sample during the period of time between collection and analysis.
In the past, plastic and glass syringes with a needle have been commonly used to collect the blood samples. U.S. Pat. No. 3,930,429 proposes a plastic syringe for distinguishing arterial pressure. However, plastic syringes have proven deficient for such purposes due to the relatively high resistance between the syringe plunger and barrel thereby making it difficult to clearly distinguish that the blood is arterial. The plunger resistance in plastic syringes prevents movement of the plunger responsive to arterial pressure alone and requires that the plunger be manually withdrawn, thus creating an undesirable vacuum in the syringe chamber during collection and requiring plunger manipulation during sampling. Further, since the plungers of plastic syringes are not sufficiently mobile to move under arterial pressure, they did not provide an indication whether arterial or venous blood is being collected. Although glass syringes may be used to detect arterial pressure, the glass syringes are relatively expensive and if the user does not exercise sufficient care, the glass syringe may be easily broken during the blood collection and transport.
Additional problems with prior blood samplers have included diffusion of oxygen and carbon dioxide though the wall of the sampler and around the plunger or venting system thereby causing erroneous readings of the blood gas analysis; the presence of either liquid heparin or air-filled deadspaces in the sampler introduces an error into the analysis of oxygen and carbon dioxide and poor thermal conductivity which inhibits rapid chilling of the sample for transport.
U.S. Pat. No. 3,943,917, entitled Method for Collecting Blood Samples, issued to Ebbe Johansen on Mar. 16, 1976, teaches a blood collection device which includes syringe housing, a plunger with a piston seal and a wedge member. The plunger is inserted into the syringe housing in order to form a collection chamber. U.S. Pat. No. 3,943,917 also teaches a procedure for collecting a blood sample in which the wedge member is inserted between the syringe housing and the piston seal of the plunger thereby deforming the piston seal in order to form a passageway so that air is allowed to escape from the collection chamber as blood enters the collection chamber.
U.S. Pat. No. 4,340,067, entitled Blood Collection Device, issued to Christen C. Rattenborg on July 20, 1982, teaches a syringe for collecting a blood sample which includes a cylindrical housing having a hollow needle at one end. A plunger slidably mounted within the cylindrical housing defines a chamber within which blood collected by the needle is received. A hydrophillic bypass element is disposed between the rim of the plunger and the inside surface of the housing to form a passageway through which air is exhausted as blood enters the chamber under arterial pressure. The passageway is automatically closed to prevent leakage from the chamber when the chamber becomes filled with blood and the hydrophillic bypass element is wetted.
U.S. Pat. No. 4,206,768, entitled Syringe Device with Means for Selectively Isolating a Blood Sample after Removal of Contaminates, issued to Donald L. Bailey on June 10, 1980, teaches a syringe device for drawing blood samples which includes an interrupter.
U.S. Pat. No. 4,326,541, entitled Syringe Device with Means for Selectively Isolating a Blood Sample after Removal of Contaminates, issued to Donald L. Bailey and Charles Williams on Apr. 27, 1982, teaches an improved syringe device for drawing blood samples.
U.S. Pat. No. 4,354,507, entitled Syringe, issued to Russell G. Raitto on Oct. 25, 1983, teaches a disposable syringe for taking arterial blood samples for blood gas testing.
U.S. Pat. No. 4,411,275, entitled Syringe, issued to Russell G. Raitto on Oct. 25, 1983, teaches a disposable syringe for taking arterial blood samples for blood gas testing.
U.S. Pat. No. 4,354,507, entitled Blood Sampling Unit, issued to Frank W. Anastasio on Nov. 30, 1982, teaches a blood sampling unit for sampling arterial blood for purposes of blood gas analysis.
U.S. Pat. No. 4,409,990, entitled Fluid Sampling Needle Assembly and Method of Use Thereof, issued to Gil N. Mileikowsky on Oct. 18, 1983, teaches a fluid transport assembly for collecting arterial blood samples.
U.S. Pat. No. 4,187,860, entitled Arterial Blood Collection Device, issued to Frank K. Villari on Feb. 12, 1980, teaches a blood collection device which includes a housing having a retention space and a hollow needle connected to a distal portion of the housing. The blood collection device has an expansible collection bag defining a collection chamber communicating with the hollow needle. The collection bag is movably responsive to arterial blood pressure between a first configuration of reduced dimensions with air substantially removed from the collection chamber and a second configuration of extended dimensions with the collection chamber enlarged to receive blood.
U.S. Pat. No. 4,266,559, entitled Blood Sampler, issued to David S. Akhavi on May 12, 1981, teaches a blood sampler which particularly suited for collecting and dispensing an arterial blood sample. A needle is connected to a flexible transparent tube that includes an air exit vent with a nonwet filter so that air, but not blood, can exit the vent under arterial blood pressure. A special needle adapter prevents formation of air bubbles, and a baffle clamp on the reservoir pinches off an air contaminated blood segment and can longitudinally strip a different blood segment which is not air contaminated. The tubular reservoir has an oxygen blocking coating, and its internal surface includes a dry anticoagulant coating.